Oxidation of uranium mononitride and uranium monocarbide

Abstract

The oxidation of uranium mononitride UN has been investigated and some comparative measurements carried out on uranium monocarbide UC. Powdered UN, of surface area 0*2-0.4m2/g, oxidizes isothermally at a measurable rate in the temperature range 230-270°C. The reaction kinetics are independent of oxygen pressure (50-760 torr) and the apparent activation energy is 30-32 kcal/mole. Complete oxidation leads to an amorphous product of composition uo3 . NO.2-0.4 * The paper is a condensed version of UKAEA Reports AERE R-4600 and AERE R-4985. 3591 * Our thanks are due to Dr. D. L. Keller and Mr. R. W. Endebrock of the Battelle Memoria Institute for supplying the ingot of UN and to Mr. B. L. Eyre of the Metallurgy Division, Hanvell, for the UC single crystals.

Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering

“…This is most likely due to oxygen pickup during transfer processes, being rapid when nitrides are exposed to air [12]. Oxygen concentrations similar to our values were found in UN pellets manufactured from metallic uranium in a similar set-up [13]. The carbon content is similar to that of the initial metallic source material, and is compatible with the value inferred from the measured lattice parameter.…”

“…When mono-and sesquinitride phases co-exist in chemical equilibrium, the N/M ratio of the latter approaches 1.54, corresponding to a theoretical density of 11.2 g=cm 3 . If on the other hand, the uranium nitride phase is adjacent to a UO 2 phase, which has formed by oxidation of UN, the N/M ratio at the interface is near 1.75 [13], giving a density of 11.5 g=cm 3 . The average areal fraction of the sesquinitride phases (or silicide phases with similar appearance in SEM) was 3:7 AE 1:0%, whereas the average areal fraction of UO 2 phases was estimated to be 4:2 AE 1:5%.…”

Phase and defect evolution in uranium-nitrogen-oxygen system under irradiation

“…Oxidation of UN powders starts at 200 °C by a slow absorption of oxygen, leading to formation of weakly crystallized U2N3 and UO2, and becomes more intensive at 250 °C accompanied by a decrease of U2N3 and appearance of -UO3 phase [54]. During the early stage of isothermal oxidation of UN powers at 260 °C, coexistence of UN, U2N3, UO2 has been observed [52]. The UN-5UO2 composite exhibits similar oxidation products during the early-stage oxidation of UN powers.…”

“…The phase evolution during oxidation of UN has been investigated since 1960s [52][53][54][55][56]. UN is converted to U2N3 and UO2 as intermediate oxidation products and ultimately to U3O8 or UO3.…”

Highly Reflective Uranium Mirrors for Astrophysics Applications

“…In contrast with nitride uranium carbides are reported to be much less stable. 18 Oxygen naturally combines with uranium surfaces exposed to the environment. The uranium dioxide formed has been used for the top layer for EUV mirrors.…”